1. Field of the Invention
The present invention relates generally to nuclear fuel rod loading systems and, more particularly, is concerned with an automated system for loading fuel rods in a desired pattern into a magazine.
2. Description of the Prior Art
Fuel assemblies in nuclear reactors of the type utilized in power generation generally incorporate numerous fuel rods arranged in spaced-apart relationship within a skeleton including top and bottom nozzles or tie plates between which the fuel rods extend. Each fuel rod generally includes a metallic tube sealed at its opposite ends by en plugs and a stack of enriched nuclear fuel pellets contained within the tube between the end plugs. All of the fuel pellets within a given fuel rod are usually of the same enrichment, but fuel rods of the same or different enrichments can be used in a particular fuel assembly depending upon the reactor type. For example, a pressurized water reactor (PWR) typically utilizes fuel assemblies with fuel rods of the same enrichment in a particular fuel assembly, whereas a boiling water reactor BWR) utilizes fuel assemblies of multiple enrichments which require the fuel rods to be arranged in a particular pattern.
It will be appreciated that fuel rod loading systems must accommodate procedures for properly identifying fuel rods of particular enrichments and for tracking them in carrying out loading of the fuel rods into the desired patterns in which they will reside in fuel assemblies. Representative prior art fuel rod loading systems are disclosed in patents to Ahmed et al (U.S. Pat. No. 4,625,396), Schoenig, Jr. et al (U.S. Pat. No. 4,649,632) and Vere et al (French Pat. No. 2,579,359).
In the fuel rod loading system disclosed by the above-cited Ahmed et al patent, which is assigned to the same assignee as the present invention, individual fuel rods have applied thereto a bar code label for identifying the enrichment of the fuel rod. An optical reader is employed by an operator for reading the identifying data on the fuel rod label. The optical reader inputs the data to a computer which compares the data with stored data for the particular fuel rod pattern of the fuel assembly to be loaded to match the fuel rod with the correct location.
Thus, to load fuel rods in the desired pattern for a BWR fuel assembly, an operator takes an individual fuel rod from a supply thereof and manually deploys the optical scanner to read and input the identifying data. The computer then displays on its screen the proper location for the fuel rod in the BWR fuel assembly. The operator then inserts the fuel rod into the location in a loading magazine which corresponds to the proper BWR fuel assembly location. The steps are repeated to complete the BWR pattern of loaded fuel rods.
The above-summarized loading system of the Ahmed et al patent is a step in the right direction toward automating the loading of fuel rods. However, the procedures required to be performed by the operator are tedious and susceptible to operator error. Consequently, a need still exists for steps toward further automation of the loading system that will reduce or eliminate entirely the opportunity for operator error.